1. Field of the Invention
The present invention relates to a current-perpendicular-to-the-plane (“CPP”) structure magnetoresistive element which allows a sensing current to flow through a magnetoresistive film, which is layered over a predetermined datum plane, and along a perpendicular direction normal to the datum plane. More particularly, the present invention relates to a CPP structure magnetoresistive element which includes an electrically-conductive free magnetic layer, an electrically-conductive pinned magnetic layer, and an electrically-conductive non-magnetic intermediate layer interposed between the free and pinned magnetic layers.
2. Description of Related Art
A CPP structure magnetoresistive element including a so-called spin valve film is known in the art. A CPP structure magnetoresistive element of the known type allows magnetization of a free ferromagnetic layer within a spin valve film to rotate in response to an applied magnetic field. In such cases, it would be preferable to previously establish the magnetization along a predetermined single direction within the free ferromagnetic layer. A pair of so-called domain controlling films are thus utilized to orient the magnetization. These domain controlling films are disposed to interpose the spin valve film over the datum plane. The free ferromagnetic layer of the spin valve film is thus located within a biasing magnetic field established between the domain controlling films.
The intensity of the biasing magnetic field, however, becomes reduced at a location more remote from the domain controlling film within the free ferromagnetic layer. A magnetic field having such a smaller intensity tends to lead to a failure to establish a unity of the magnetization, or a single magnetic domain, within the free ferromagnetic layer. A biasing magnetic field of a sufficient intensity cannot therefore be obtained without further reducing the size or width of the spin valve film. Additionally, such domain controlling films suffer from less accuracy in form or shape in a production process. Since the intensity of the biasing magnetic field tends to be influenced by the form or shape of the domain controlling films, it has been difficult to obtain a stable biasing magnetic field according to the conventional method.
Spin valve films are generally made of electrically-conductive materials. Sensing currents are therefore able to flow through anywhere in the entire spin valve film. Accordingly, it has been impossible to reduce the path of the sensing current within the spin valve film unless the spin valve film is also reduced in size. A reduced path of the sensing current can lead to a higher sensitivity of the CPP structure magnetoresistive element. Also, a reduced sensing current path can lead to a reduced effective width of a magnetic core, which serves to improve the resolution when the CPP structure magnetoresistive element is used to read magnetic information.
Accordingly an object of the present invention is to provide a CPP structure magnetoresistive element which can sufficiently establish a single magnetic domain within a free magnetic layer without having to further reduce the size of a magnetoresistive film.